The present invention relates to a multiple canister mount, and more particularly to a canister mount for a protective mask or the like which will consecutively receive canisters having bolt connectors of differing size and/or differing thread form.
A protective mask which is currently used extensively by military and civilian organizations has a flexible face covering which is strapped in an airtight fashion to the face of the wearer. Components of the mask secured to the flexible face covering include transparent viewing means, an outlet valve and speech unit and removable canister filled with charcoal or a similar absorbant substance releasably secured in airtight fashion to an appropriate mount means secured to the mask, through which canister during operation outside air is purified as it is drawn through appropriate valve means into the interior of the mask.
At the present time different countries manufacture different types of such masks and respirators and there are consequently different sizes of canister connectors and canister mount means therefor.
Attempts have been made to standardize these canister connectors and canister mounts. For example, NATO countries have recently agreed to a standardization program for canisters and protective masks and respirators aimed at creating a single size of canister bolt connector having a standard thread form, which would be received in a correspondingly sized and threaded canister mount in the protective mask or respirator. According to the agreement reached, the threaded connection for the attachment of the canister of the protective mask must allow physical interchangability between the mask and canister, and the threaded connection must provide an airtight joint between the canister and the mask. Also the removal and replacement of the canister should not require tools of any kind.
Thus, while new canisters of a standard size and new masks which are now being made may conform to the terms of such an agreement, many "old" masks and canisters are still in use. Thus, a means of converting the canister mount of such old masks to receive canisters having a different sized and threaded connector (e.g. that proposed in the NATO standardization program) would be very desirable. Additionally, it would be desirable if a means could be provided which would adapt "new" masks manufactured according to such NATO standards to receive, alternatively, canisters having bolt connectors sized and threaded differently from such standard bolt size and thread, for example canisters of a different size and thread form which might be still readily available.
One proposal along these lines, to provide interchangability of connectors and masks while the change to the standard is taking place, has been to develop an adapter, one side of which has a bolt connector and a thread form to be threaded into one size of canister mount (e.g. that of old masks), and the other side of which has a threaded socket of a size and form to receive the bolt connector of canisters conforming to the new standard. Such adapter however has presented several practical problems which reduce its practicality. Because of its nature, it results in a canister being secured to the mask at a greater distance from the mask than one which is secured to the original canister mount of the mask, the canister thereby being more exposed as an obstruction and creating greater "assymetric loading" and consequently increasing the risk of breaking the peripheral face seal which must exist when the mask is worn, if such a mask is to effectively shield the face of the wearer against noxious or lethal gases. Also, when the wearer changes canisters, if such an adapter is used, the adapter must be normally held in place to prevent it becoming unscrewed while the old canister is being removed. Such a procedure is an awkward one for a person to carry out in the field and indeed, should the adapter become loose or removed while the canister changing is taking place, obvious dangers to the wearer, who must hold his breath during such operation, exist. This operation in some conditions (e.g. wartime conditions in the presence of certain types of gases) must be carried out with the wearer having gloves on, further complicating the operation. Additionally, such an adapter is a relatively small article and subject to loss by an individual carrying it.
It is an object of the present invention to provide a "universal" canister mount for a protective mask or the like which will receive at different times canisters having different sized and threaded bolt connectors. It is a further object of the present invention to provide such a canister mount which will remove the need for a separate adapter to achieve such end.